Muffler



" Jan. 30, 1968 F. J. GRE lPEL ET AL MUFFLER Filed Aug. 20, 1965 INVENTOR5 FRANK J. GREIPEL MICHA EL l/V. Ros/v51? W+Bwad I AT o /vsKr United States Patent 3,365,863 MUFFLER Frank J. Greipel and Michael W. Rosner, St. Paul, Minn, assignors to Bjork and Johnson, Inc., St. Paul, Minn., a corporatiouof Minnesota Filed Aug. 20, 1965, Ser. No. 481,285 7 7 Claims. 01. 55-276) This invention relates to a mufller for attachment to the exhaust manifold of an automotive engine or similar internal combustion engine for the reduction of objectionable constituents, such as unburned hydrocarbons and carbon monoxide, emitted from the exhaust system of the engine.

The exhaust gases from the average automobile and similar internal combustion engine contain a mixture of carbon monoxide, carbon dioxide, unburned or partially burned hydrocarbons, nitrogen, some of the nitrogen oxides, and under certain conditions, portions of unconsumed air. It is reasonably well established that these automobile exhaust gases and similar exhaust gases from other internal combustion engines contribute to the production of smog. In certain urban areas smog is produced in such quantities as to be considered objectionable and potentially harmful. As a result, states have begun to legislate against the introduction into the atmosphere of gases which contribute to smog production. Exemplary of this is legislation enacted in California Which establishes a maximum permissible content of hydrocarbon in escaping automobile exhaust of 275 parts per million and maximum carbon monoxide content of 1.5 percent. More stringent requirements have been proposed by which maximum permissible hydrocarbon would be reduced to 180 ppm. and maximum carbon monoxide to 1.0 percent.

Prior attempts to reduce the unburned hydrocarbon and carbon monoxide content in automobile exhaust have principally been in the form of so-called after burners for direct oxidation of the undesired materials with excess air at high temperatures above about 2000 F. and catalytic converters for catalytically oxidizing the unwanted materials with excess air at lower temperatures of the order of 500? F. However, neither of these systems has proved completely satisfactory under the wide variety of operating conditions which must be met in the course of operation of an automobile in normal use.

In a copending application of Gust H. Bjork, Ser. No. 268,334, filed Mar. 27, 1963, and now Patent No. 3,232,- 373, issued Feb. 1, 1966, owned by the assignee of the present application, there is disclosed an anti-pollution muifier with transverse expanded metal battles. The present invention constitutes a modification of and improvement over the mufiler of that prior copending application.

The-principal object of this invention isto provide a relatively simple muflfler system for exhaust gases from internal combustion engines to effectively reduce the content of objectionable gaseous constituents as well as to reduce noise.

The invention is illustrated by the accompanying drawings in which the same numerals refer to corresponding parts and in which;

FIGURE 1 is a side elevation of a mufiler according to the present invention partly in section and partly broken away to better show interior construction;

FIGURE 2 is a transverse section on the line 2-2 of FIGURE 1 and in the direction of the arrows;

FIGURE 3 is a transverse section on the line 3-3 of FIGURE 1 and in the direction of the arrows;

FIGURE 4 is a transverse section on the line 4-4 of FIGURE 1 and in the direction of the arrows;

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FIGURE 5 is a transverse section showing an alternative form of internal muffler structure; and

FIGURE 6 is a transverse section on a reduced scale showing a further modified form of interior structure.

Referring now to the drawings, the muffler according to the present invention includes an elongated tubular housing, indicated generally at 10 and constructed of heat resistant metal. The housing has an inlet 11 of reduced diameter at one end for receiving obnoxious exhaust gases from an internal combustion engine and a similar outlet 12 of reduced diameter at the opposite end of the housing for discharge of purified exhaust gases.

Immediately adjacent the inlet 11 there is desirably disposed an optional aspirating unit comprising a hollow tubular ring 14. Ring 14 extends around the inner periphery of housing 10 adjacent its end wall, extending transversely relatively to the longitudinal axis of the housing. The innermost periphery of tubular ring 14 is provided with a plurality of apertures 15. A connection or fitting 16 communicates with the ring 14 and extends through the housing wall.

When fitting 16 is open to the atmosphere the flow of exhaust gases through inlet 11 and ring 14 causes an aspirating effect by which fresh air is drawn into the muffler and intermingled with the exhaust gases and assists in the reduction of the objectionable constituents. Alternatively, the fitting 16 may be connected to the engine crankcase to draw crankcase fumes into the muffier for combustion and discharge, or it may be connected to a supply vessel of liquid purifying chemical.

Disposed in the housing 1% adjacent the inlet 11 and immediately downstream from the aspirating unit is a transverse disc of openwork screening 17 formed from a heat resistant metal, such as stainless steelv The disc 17 and other apertured discs hereinafter referred to are conveniently formed from so-called unfiattened expanded metal sheeting which is produced by forming a series of staggered slits in an impervious metal sheet and then stretching the sheet in a direction perpendicular to the slits to open the slits into apertures and expand the metal sheet in that direction while contracting it slightly in the opposite direction. The stretching operation by which the metal sheet is expanded imparts a twist or bend to the ribbon-like portions of the metal sheets separating the apertures. This twisting o-r bending of the ribbon-like metal members between adjacent apertures imparts an angle or oblique direction to the aperture itself. The expanded metal sheeting is unflattened to preserve the oblique apertures.

The discs may likewise be formed from so-called louvertype screening or the oblique apertures may be drilled or punched through metal sheeting at an acute angle relative to the plane of the sheet. The oblique apertures serve the function of altering the straight linear line of exhaust gases and thereby lengthen the path of travel through the muffler device. While use of screening with oblique apertures is not essential to the construction of the device according to the present invention, it is desirable.

Immediately downstream from apertured disc 17 is a central longitudinal tube 18 which is generally coaxial with housing 10 and extends for about 40 to 60 percent of the length of the housing. Tube 18 defines an annular space 19 between the outer wall of the tube and inner wall of the housing. Tube 18 is held in the center of the housing by means of a plurality of strut or spacers 20-, in this instance in the form of screws securing a plurality of elongated longitudinal tubular ducts 21 to the outside surface of tube 18. Tubular ducts 21 are spaced evenly about the periphery of tube 18. The diameter of each tube 21 is less than the depth of annular space 19.

The plurality of tubes 21 forms a framework about which stainless steel wire is wound in a tight coil 22 of single strand thickness. As best seen in FIGURE 3, wire winding 22 serves to divide the annular space 19 into a plurality of inner longitudinal ducts 23 defined by the outside of tube 18, the outside of adjacent pairs of tubes 21 and the inside of winding 22, and a surrounding outside generally annular duct 24 defined by the outside of the winding and inside of the housing wall.

A cylindrical cup 25 having a closed end and cylindrical side walls is inverted over the downstream end of tube 18 within the housing. Cup 25 is supported substantially coaxially with housing and tube 18 by being attached to a rigid transverse apertured disc or screen member 26, which is similar to disc 17. Cup is of larger diameter than tube 18, but of lesser diameter than housing 10, so that it defines with the housing Wall a relatively short annular passage 27 through which all of the exhaust gases must pass. The closed end wall of cup 25 is spaced from the end of tube 18. Thus, all exhaust gases which pass through tube 18 are diverted back by means of cup 25 into ducts 21 or 23.

Downstream from annular passage 27 and disc 26 are a plurality of generally similar screen and baffle plate units 28A and 28B alternating with one another. Each unit is composed of a pair of dished apertured discs 29 and 30 disposed on opposite sides of a flat apertured disc 31 half of whose area is covered by a semi-circular bafile plate 32. Discs 29, 30 and 31 are formed from openwork screen sheets, such as expanded metal as described. They are formed from heat resistant material such as stainless steel. The dished discs 29 and 30 are disposed on opposite sides of flat disc 31 with their concave surfaces facing inwardly toward one another and their peripheral edges abutting the peripheral edge of the fiat dsic. The convex surfaces of adjacent dished discs of the alternating units 28A and 28B abut one another and in this manner maintain spacing between the flat discs, and particularly between the bafiie plates 32.

It will be seen that the alternating bathe plates 32 are disposed as to define a tortuous or zigzag passage. Assuming a centerline plane through housing 10, then each unit 28A is disposed with the baflle plate on one side of that plane and each unit 28B is disposed with the baffle plate on the opposite side of the plane. In order to maintain the units in these relative positions each disc is provided with a keyway, as best seen at 33 in FIGURE 4, which engages an elongated key member 34, which may be a rod or bolt or may be a rib formed on the inside Wall of housing 10. It does not matter whether the units 28A and 28B may rotate within the housing so long as they maintain their positions relative to one another.

The apertured discs are desirably formed with oblique apertures and these are desirably disposed so that the apertures in alternating discs direct the gas flow through them in different directions in order to extend the length of the path gases must travel through the mufiler. For example, the apertures in disc 31 are desirably disposed so as to direct the gases passing through it in an angular direction toward the next adjacent downstream bafiie plate, rather than toward the openwork segment adjacent that bafile plate. An apertured end disc 35 serves as a retainer for the units 28A and 28B and final diffusion member for the purified exhaust gases before they are discharged through outlet 12.

In FIGURE 5 there is shown an alternate form of construction for supporting the wire winding. According to this form of the invention central tube 18A is formed with a plurality of radiating fins 36 which are desirably integral with tube 18A and formed by extrusion. At each end fins 36 are provided with an extension or projection 37 which serves to hold tube 18A spaced centrally within housing 10. The fins 36 in turn serve as a support for winding 22A of stainless steel wire similar to that already described. A plurality of inner longitudinal ducts or channels 23A are formed between the outer wall of tube 18A, fins 36 and the inner surface of wire winding 22A and an outer annular duct or channel 24A is formed between the outer surface of winding 22A and the inside wall of housing 10.

In FIGURE 6 there is shown a further modified construction of the support for the wire winding. A plurality of longitudinal ducts 38 of generally triangular crosssection are formed around tube 18 by pleating a sheet of heat resistant metal 39 and wrapping it about tube 18. Suitable spacing members or struts 40 at the opposite ends of tube 18 hold it spaced centrally within housing 10. Wire winding 22B is formed around the edges of the pleated members. A further set of inner longitudinal ducts or channels 238 are formed between the outside walls of ducts 38 and the inside surface of the wire winding and a further outer annular channel 24B is between the outer surface of the winding and inner wall surface of the housing.

In the operation of the muffler according to the present invention the exhaust gases from an internal combustion engine are introduced through inlet 11 into housing 10. The main thrust of the exhaust gases is through central tube 18. Where aspirating unit 14 is included, air or other gases or chemicals are admixed and intermingled with the exhaust gases. The flow of exhaust gases through tube 13 is then diverted and reversed by means of cup 25 and most of the gas is directed back upstream through the ducts surrounding the central tube and then back downstream in the annular chamber 24 between the wire winding 22 and inner housing Wall. Most of the purification of the gas fumes and reduction of unburned hydrocarbons and carbon monoxide occurs up to this point in the passage of the fumes through the mufiler. The gases then pass through the annular duct 27 into the tortuous path through screen and bafile units 28A and 28B where further purification and noise abatement take place.

The manner in which the structure of this mufiler effectively reduces polluting contaminants in exhaust fumes is not fully understood. It is theorized that the wire winding heated to glowing heat by the hot exhaust gases catalyzes or otherwise accelerates the oxidation of the contaminants. Maximum contact between the fumes and glowing stainless steel is maintained by the tortuous path of the gases through the muffier. The effect is continued in the passage of the gases through the screen and baflle units in the downstream end of the mufiier. The exhaust gases are at a temperature of the order of about 1600 to 2000 F. at the time they enter the mufiier. All of the components of the muffler are constructed from materials capable of withstanding these temperatures.

We claim:

1. A pollution reducing mufiier for an internal combustion engine comprising:

(A) an elongated tubular housing of heat resistant metal,

(B) a reduced diameter exhaust gas inlet at one end of said housing and a reduced diameter purified gas discharge at the other end thereof,

(C) a central coaxial tube of heat resistant metal disposed within said housing adjacent the inlet end,

(D) a first annular space between said tube and housing wall,

(E) a closed end cylindrical cup of heat resistant metal disposed within the housing inverted over the downstream end of said tube,

(F) said cup being coaxial with said tube, of large diameter than said tube and lesser diameter than said housing to define a second shorter annular space of lesser depth than said first annular space between the cup and housing wall, said cup having its bottom end spaced from the downstream end of said tube,

( G) a plurality of longitudinal ducts within said first annular space between said tube and housing wall, said ducts being spaced about the periphery of said tube and spaced inward from the housing wall,

(H) a tight winding of stainless steel wire surrounding said ducts, said wire being spaced outward from said tube and inward from the housing wall, and

(I) a multi-screened tortuous gas passage from said second annular space to the discharge end of the housing.

2. A muffier according to claim 1 further characterized in that an aspirating device is disposed within said housing at the inlet end thereof, said device comprising a tubular ring extending around the inside wall of the housing, a connection to said ring extending through the housing wall and a plurality of spaced apertures through the wall of the tubular ring extending around the inner periphery thereof.

3. A rnufiler according to claim 1 further characterized in that said tortuous gas passage includes a plurality of transverse bafile plates each extending across approximately one half of the cross-section of the housing, said baffle plates being spaced longitudinally and alternating bafiie plates being disposed on opposite sides of a longitudinal plane extending along the axis of the housing.

4. A mufller according to claim 3 further characterized in that a segment of open mesh metal screening is disposed generally coplanar with each baffle plate in the space extending across the approximately one half of the crosssection of the housing which is not covered by the bafile plate.

5. A muffler according to claim 4 further characterized in that said screening includes a plurality of ribbon-like portions interconnected so as to define a multitude of closely spaced apertures uniformly distributed across the area of the screening, each of said ribbon-like portions being disposed obliquely at an acute angle relative to the plane of the screening thus defining apertures extending obliquely at an acute angle relative to the plane of the screening, said apertures in each alternating segment of screening being directed in an angular direction toward the next adjacent downstream baflie plate.

6. A mufiler according to claim 4 further characterized in that said baffle plates and planar screening segments are held spaced apart by dished open mesh metal screening discs alternately disposed with their convex surfaces abutting one another and with their peripheral edges abutting alternating bafile plates and planar screening segments.

7. A mufiler according to claim 4 further characterized in that said tube is composed of a copper containing metal and said baflie plate and screening segments are composed of stainless steel.

References Cited UNITED STATES PATENTS 887,988 5/1908 Wakley et al. 1,484,526 2/ 1924 OConnor. 2,511,713 6/1950 Hoyle et al. 2,537,217 1/1951 Farr 488 2,683,444 7/ 1954 Miller. 3,042,138 7/ 1962 Reinert. 3,232,373 2/1966 Bjork 181-36 HARRY B. THORNTON, Primary Examiner.

S. W. SOKOLOFF, Assistant Examiner. 

1. A POLLUTION REDUCING MUFFLER FOR AN INTERANL COMBUSTION ENGINE CCOMPRISING: (A) AN ELONGATED TUBULAR HOUSING OF HEAT RESISTANT METAL, (B) A REDUCED DIAMETER EXHAUST GAS INLET AT ONE END OF SAID HOUSING AND A REDUCED DIAMETER PURIFIED GAS DISCHARGE AT THE OTHER END THEREOF, (C) A CENTRAL COXIAL TUBE OF HEAT RESISTANT METAL DISPOSED WITHIN SAID HOUSING ADJACENT THE INLET END, (D) A FIRST ANNULAR SPACE BETWEEN SAID TUBE AND HOUSING WALL, (E) A CLOSED END CYLINDRICAL CUP OF HEAT RESISTANT METAL DISPOSED WITHIN THE HOUSING INVERTED OVER THE DOWNSTREAM END OF SAID TUBE, 